Hello,
I want to create a small multiplayer game where Players can create their private servers with passwords and other players can join them. I have no experience with multiplayer tools.
The best example I can give is CS Go where players can host servers on PC and their friends can join them
Thanks for announcing this!
Or did you mean to ask a question? 
Sorry, If I was not clear in what I was saying. What is the best method to create a p2p multiplayer in unity? Please help
Again, far too vague. You are literally asking something like „What‘s the best wheel for driving?“ and we can‘t even tell whether you mean steering wheel, drivewheel or actual wheels.
What‘s your intention? Your requirements? What are you uncertain about? If you can‘t answer these use whatever comes to your mind because it will largely not matter.